Adsorbent materials having magnetic properties are known. Often magnetic properties such as ferromagnetism and superparamagnetism are desired to enable use of magnetic fields in various processes. Superparamagnetism is of special interest in many chemical applications where it is desired to collect and redisperse adsorbent particles. The particles of the prior art generally comprise a superparamagnetic material (e.g. magnetite) which is enveloped in or treated with some diverse material.
For many applications, the materials of the prior art have been considered adequate, however for certain applications, the materials of the prior art are inadequate due to their vulnerability to leaching in acidic environments or their lack of sufficient magnetic performance. In many applications such as processing of edible substances or sensitive biological materials (e.g. nucleic acid purification such as described in published patent application W095/06652), these deficiencies result in poor performance or simply prohibit use of these materials.
Thus, there is a need for improved coated superparamagnetic particles, especially particles useful as superparamagnetic adsorbents. Further, there is a need for improved methods of making such adsorbents.